1. Field of the Invention
The present invention relates to implantable drug delivery devices for infusing a therapeutic agent into an organism, and more particularly, relates to an improved bulkhead, which is the main structural component of an implantable drug delivery device, having integrated subsystems. The invention additionally contemplates a related method of manufacturing implantable drug delivery devices, which simplifies manufacturing and assembly processes thereby reducing the overall cost of production.
2. Description of the Related Art
Implantable drug infusion devices are well known in the art. These devices typically include a medication reservoir within a generally cylindrical housing. Some form of fluid flow control is also provided to control or regulate the flow of fluid medication from the reservoir to the outlet of the device for delivery of the medication to the desired location in an body, usually through a catheter. These devices are used to provide patients with a constant and long term dosage or infusion of a drug or other therapeutic agent. Over time, the drug or other sterile solution becomes depleted and it is necessary to refill the device with a new supply of drug. This is commonly done by providing the device with a fill port that is typically covered with a resilient resealable septum which is accessible by injecting a hypodermic needle through the skin and into the septum thereby providing access to refill the reservoir.
Implantable infusion devices may be categorized as either passive or active. Passive drug infusion devices rely upon a pressurized drug reservoir to deliver the drug. Thus, such devices tend to be both smaller as well as cheaper as compared to active devices. An example of such a device includes the Medtronic IsoMed. This device delivers the drug into the patient through the force provided by a pressurized reservoir applied across a flow control unit.
Active drug or programmable infusion devices feature a pump or a metering system to deliver the drug into the patient""s system. An example of such a drug infusion pump currently available is the Medtronic SynchroMed programmable pump. Additionally, U.S. Pat. No. 4,692,147 (Duggan), assigned to Medtronic, Inc., Minneapolis, MN., discloses a body-implantable electronic drug administration device comprising a peristaltic (roller) pump for metering a measured amount of drug in response to an electronic pulse generated by control circuitry associated with the device. The applicant specifically incorporates U.S. Pat. No. 4,692,147 (Duggan) by reference.
Such devices include a drug reservoir, a fill port, a pump to pump out the drug from the reservoir, and a catheter port. A catheter, connected to the catheter port, transports the pumped out drug from the device to a patient""s anatomy. Such devices also typically include a battery to power the pump as well as an electronic module to control the flow rate of the pump. The drug reservoir, fill port, pump, and catheter port are generally held in a housing, commonly called a chasis or bulkhead, which is the main structural component of the drug infusion pump. The bulkhead typically has a series of passages from the drug reservoir and through the pump that lead to the catheter port which is located on the side of the housing.
It is advantageous to provide an implantable drug infusion devices with a means for injecting medication or other therapeutic agents directly into the catheter. In such instances, a catheter access port may be provided in addition to the fill port. The catheter access port will generally have a resilient resealable septum that is accessible percutaneously by hypodermic needle. This septum provides direct access to the catheter bypassing the primary fluid passageway and allows the medication to be administered directly into the body at the site of the catheter. Alternatively, the catheter may be used to remove or extract fluids, such as blood, from a patient.
Prior art implantable drug delivery devices are typically cylindrical in shape. These devices typically include a top shield, a bottom shield, and a bulkhead. The bulkhead is typically disk-shaped. Attached to the bulkhead are various subassemblies. Catheter access ports, filters, over pressure mechanisms, fill ports, and pump mechanisms are examples of such sub-assemblies. A disk-shaped bottom shield is connected to the bulkhead and forms a space for a drug reservoir. A bellows may be located in this space. After the pump components, battery and electrical components, and subassemblies are connected to or placed within the bulkhead, the top and bottom shields are attached to the bulkhead. The top shield, bottom shield, and bulkhead combine to form a hermetic enclosure.
While the prior art devices operate satisfactorily, they are relatively expensive to manufacture and to assemble. Certain disadvantages associated with the design of prior art devices contributes to the expensive of manufacturing and difficult assembly of prior art devices. In particular, bulkheads for implantable drug infusion pumps do not fully integrate all subassemblies into the bulkhead. Rather, certain subassemblies are separated from the bulkhead and attached to the bulkhead during assembly. For example, in the SynchroMed and other prior art drug infusion devices, the catheter access port is a separate component that is attached to the outside of the bulkhead portion of prior art drug infusion devices. Attaching the catheter access port requires additional and often expensive and complicated manufacturing steps. Typically, a catheter access port is either welded or attached with a silicone medical adhesive to the outside of the bulkhead. Attaching other subassemblies to the bulkhead results in similar added expense and manufacturing complexities.
The present invention provides an implantable drug infusion device which features a bulkhead having integrated subsystems. By integrating subassemblies, into the bulkhead, manufacturing efficiencies are created. For example, integrating the catheter access port into the bulkhead eliminates the manufacturing step of welding the catheter access port to the bulkhead from the assembly of implantable drug infusion pumps. Thus, the present invention provides significant cost-savings opportunities and creates fewer production problems.
The manufacturing benefits achieved by the integration of subassemblies into the bulkhead include: a reduction in the number of components to assemble, an elimination the number of manufacturing steps, and a reduction in manufacturing costs. Another advantage of the present invention, greater control and accuracy in the connections between the various subassemblies, results from integrating the fluid system into the bulkhead. Thus, the present invention eliminates the expense and assembly difficulties associated with prior art drug infusion devices while improving the accuracy of the drug dosage delivered by the pump.
In a preferred embodiment, the catheter access port is integrated into the bulkhead. This eliminates the need to manufacture this as a separate component and eliminates the manufacturing step of attaching this component to the completed assembly. In addition to integrating the catheter access port features into the bulkhead, the preferred embodiment of the bulkhead of the novel drug infusion device has key features of other subassemblies built into it. For example, portions of the pump, pump race, fill-port, over pressure mechanism, filter, and fluid pathway features of other subassemblies may be advantageously integrated into the bulkhead.
In another preferred embodiment of the present invention, the entire fluid pathway is integrated into the bulkhead. This can be readily accomplished by simple drilling and/or surface milling operations so that precise manufacturing and assembly may be achieved and greater control and accuracy of the connections between subassemblies achieved. Greater control of these connections allows for a more precise metering of medication through the device.